This invention relates to integrated circuits, and more particularly, to operating a safety function including the execution of test functions on an integrated circuit.
A safety function or a safety critical application is an application whose failure may have considerable and often unacceptable consequences including substantial economic and financial damage, extensive damage to the environment, and loss of life. Many safety critical applications rely on or are implemented on integrated circuits, and operating a safety function generally requires testing the integrated circuit's integrity at regular safety test intervals.
An integrated circuit that enters a safety test interval is often required to leave the user mode in which the safety function is executed and to enter a test mode in which the integrated circuit and potentially all the devices chat are coupled to or controlled by the integrated circuit are forced offline. After entering test mode, a test function is executed which verifies the correct operation of the integrated circuit.
The test function is often implemented with limited reliance upon external control and test equipment and is sometimes referred to as a built-in self-test (BIST). Executing a BIST can consume a significant amount of time due to the high degree of coverage required by the BIST. The duration of the BIST usually increases with the complexity of the tested integrated circuit and the frequency at which the test function is required to be executed.
Consequently, a lot of time and resources are eventually wasted during the execution of the test function during which the integrated circuit and potentially all devices that are coupled to or controlled by the integrated circuit are idle.